1. Field of the Invention
This invention relates to a circuit for the protected alternating current power supply of an electrical load, this circuit including an electromechanical protective circuit breaker and a bi-directional electronic switch positioned in series, downstream from the protective circuit breaker and driven by a command device in order to provide a graduated operation of the load, and a shunt contactor which ensures a continuous operation of the load is mounted in parallel to the electronic switch.
2. Discussion of the Background
Such a circuit is known from Patent Application EP 633584. The electronic device is used for the progressive starting and stopping periods of the load while the shunt contactor is used outside these periods in order to prevent heating up of the electronic switch.
The role of the protective circuit breaker is to protect the principal current path in the event that a fault current is detected; its response time is however too long to effectively protect the electronic switch or the shunt contactor during operation.
In order to remedy this disadvantage, it is known, on the one hand, to shunt the electronic switch with a spark gap device in order to divert the current, and on the other hand, to oversize the shunt contactor in order to avoid welding of the contacts.
Oversizing the shunt contactor nevertheless poses a problem of space and of cost.